Delph retired aged 32 despite playing 11 Premier League games that season...
I guess money is why players dropping down the leagues is so rare these days. No need to do it anymore.
Mark Walters was my favourite player when I was younger but you just don't see those sorts and we were still in the Championship I suppose. Matty Taylor is probably the closest since then for a 'Premier League quality' player.
Although Charlie probably fits the bill...
Most are financially set by the time the top paying clubs are done with them. From there it all comes down to how much love for the game do they have? Its either a massively reduced wage in the lower leagues or a bit of a lesser wage and moving to another country.